1. Field of the Invention
The invention relates generally to soil compaction testing equipment and methods for testing the compaction of soils. In particular aspects, the invention relates to devices and methods for determining the soil modulus of soil.
2. Description of the Related Art
Traditionally, techniques for controlling and monitoring the degree of compaction for soils have involved the measurement of dry density for the soil and the determination of an optimum water content for the soil. The term “soil,” as used herein, is intended to apply to a wide variety of substances that are intended to be compacted to a specific degree of density in the course of typical civil construction works, including natural soil, base courses, asphalt, embankments and retaining wall backfill. Using conventional methods for monitoring dry density of the soil, a sample of compacted soil is placed inside a cylindrical steel mold. The weight and water content of the sample are determined in a laboratory. A graph is then generated that plots dry density against water content. From these calculations, a maximum dry density and optimum moisture content are derived.
There has been a recent movement to utilize a soil modulus, rather than dry density, as a measure of soil compaction. One reason for this is that soil modulus is currently used as a basis for overlying pavement upon a subbase of soil. One new tool that is used to measure soil modulus is the H-4140 Geogauge™, or Humboldt Stiffness Gauge, from Humboldt Manufacturing Co. of Norridge, Ill. This device places a toroidal-shaped plate upon the soil to be measured and then induces vibration in the plate using a shaker apparatus. Unfortunately, the Geogauge™ device is expensive and complex.
There is a need to provide improved methods and devices for compaction testing and particularly for measurement of soil modulus. The present invention addresses the problems of the prior art.